A scanning electron microscopy evaluation of the cleanliness of un-instrumented areas of canal walls after root canal preparation

Introduction: Cleanliness of the canal space is the ultimate goal of its preparation. Nevertheless, some portion of the canal walls are left un-instrumented during preparation. Therefore, the aim of this ex vivo study was to evaluate the cleanliness of un-instrumented canal walls after root canal preparation for the presence or absence of debris and smear layer. Materials and Methods: A total of 24 single-rooted extracted teeth were prepared with the crown-down technique using Protaper universal rotary file system. Micro-computed tomography (micro-CT) was used to scan the specimens before and after instrumentation. The un-instrumented area was measured and localized. The roots were split longitudinally and then subjected to scanning electron microscopy (SEM). The presence of debris and smear layer in the instrumented and un-instrumented areas of the canal were evaluated by analysing the SEM images with a five-score evaluation system based on the reference photographs. Results: High levels of root canal cleanliness (≤ score 2) were found for the instrumented areas were detected (P = 0.003). Conclusions: Under the condition of this study, un-instrumented areas of the canal were less clean in comparison to instrumented portion.